Silicon carbide particulates incorporated into microalloyed steel surface using TIG: microstructure and properties

Surface metal matrix composites have been developed to enhance properties such as erosion, wear and corrosion of alloys. In this study, ~5 µm or ~75 µm SiC particulates were preplaced on a microalloyed steel. Single track surface zones were melted by a tungsten inert gas torch, and the effect of two heat inputs, 420Jmm-1 and 840 Jmm-1,compared. The results showed that the samples melted using 420Jmm-1 were crack-free. Pin-on-disk wear testing under dry sliding conditions were conducted. The effects of load and sliding velocity were used to characterise the performance of the crack-free samples. Microstructural and X-ray diffraction studies of the surface showed that the SiC had dissolved, and that martensite, was the main phase influencing the hardness

Influence of shielding gases on preheat produced in surface coatings incorporating SiC particulates into microalloy steel using TIG technique

The use of a tungsten inert gas (TIG) welding torch has resulted in the development of an economical route for surface engineering of alloys, giving similar results to the more expensive high power laser. Due to the preheating generated by both techniques, the extent of the temperature rise is sufficient to produce significant changes to the melt dimensions, microstructure and properties between the first and last tracks melted during the coating of a complete surface. The present study examines if similar changes can occur between the start and finish locations of a single track of 50 mm length. The results show that for a TIG melted surface of a microalloy steel substrate, with or without incorporating preplaced SiC particles, in either argon or argon-helium environments, a maximum temperature of 375°C developed in the second third of the track. Even over this short distance, a hardness decrease of >300 Hv was recorded in the re-solidified SiC coated substrate melt zone, microstructure of a cast iron with cracks were observed. Also porosity was found in all the tracks, with and without preplaced SiC powders

Role of preplaced silicon on a TIG processed SiC incorporated microalloyed steel

Research aimed at enhancing the surface properties of carbon steels by incorporating fine silicon carbide particulates has had limited success because the dissolution of the ceramic occurred. This research considers a method of reducing SiC dissolution by generating a high Fe–Si liquid which protects the ceramic. Three particulate groups were investigated, (1) ∼ 5 µm SiC, (2) ∼45 µm Si +∼ 5 µm SiC, and (3) ∼45 µm Si, all incorporated into a microalloyed steel using a tungsten inert gas process. Detailed microhardness of the melt zones together with microstructural analysis showed that the addition of Si resulted in a cracked hard layer containing SiC. However, in Specimen 1, a thicker, hardcrack-free layer resulted from the microstructure developed by the dissolution of SiC